Computer Science - Paper 1
What is a computer?
A electronic device that takes input, processes data and delivers an output.
What is a program?
A set of instructions.
What are computer systems made up of?
Computer systems are made up of hardware and software which work together.
What is hardware?
Hardware is the physical components of the computer.
What is primary storage?
The memory in which the computer can store the data or instructions that are currently in use.
Is primary storage and secondary storage hardware or software?
Hardware.
What are the different types of primary storage?
Random access memory (RAM) & Read only memory (ROM).
What is secondary storage?
The memory in which the computer can store the data or instructions which are not currently in use.
What are the main types of secondary storage?
Hard disk drives (HDD), Solid state drives (SSD), Compact disk (CD), Flash (USB drive).
What is a processor?
A component that processes data and instructions to control other components within the computer.
Is a processor hardware or software?
Hardware.
What are the different types of processors?
Central processing unit (CPU) & Graphic processing unit (GPU).
What are input/output devices?
Allow users to input data into the computer or receive a data output from the computer.
Name some examples of I/O devices.
Keyboards, Mouse, Speakers.
What is a general purpose system?
A computer system that can be programmed to perform many different tasks.
Name some examples of general purpose systems.
Smartphones, PCs.
What is a embedded system?
A computer system with a dedicated function within a larger device.
Name some examples of embedded systems.
Traffic lights, Sat-navs, Calculators.
What does Von Neumann architecture consist of?
ALU, CU & Registers.
What is an ALU?
Part of the CPU that performs all off the arithmetic and logical decisions.
What is an CU?
Sends control signals to other components to control how data moves around the CPU.
What is a clock?
Coordinates the CPUs activity.
What is a decoder?
Decodes a programs instructions.
What are the main components of the CU?
Clock & Decoder.
What are registers?
Super-fast pieces of onboard memory inside the CPU, each with a specific purpose.
What is a MDR?
Holds the data that has been retrieved from the memory or that is about to be stored in the memory.
What is a MAR?
Holds the address of the location in the memory where data is to be retrieved or stored.
What is an accumulator?
Accumulator (ACC) = Holds the result of the calculation and operations performed by the ALU.
What is a PC?
Holds the memory location address of the next instruction to be performed by the CPU.
What are the different types of registers?
MAR, MDR, ACC, PC
What is the 'fetch' in a FDE cycle?
Fetches the next instruction from the main memory (RAM, and then brings it back to the CPU.
Describe the 'fetch' process from the FDE cycle.
The address of the next instruction that needs to be processed next is copied from the PC to the MAR.
The PC is then incremented to the next instruction that will be needed when the cycle starts again.
The instruction stored at the location held by the MAR is copied to the MDR.
What is the 'decode' in a FDE cycle?
Inspects the instruction and works out what it needs doing.
Describe the 'decode' process in the FDE cycle.
The CU decodes the instruction and sends control signals to the component that needs to act.
What is the 'execute' in a FDE cycle?
Carries out the instruction.
Describe the 'execute' process in the FDE cycle.
The operation indicated by the instruction is performed by the appropriate component.
Why don't all CPUs execute code at the same time?
As some processors may be faster due to certain factors such as the number of cores, clock speed and the size of the cache.
What is cache memory?
Fast memory inside the CPU which stores frequently used data and instructions.
Name some factors of the cache.
Much quicker than getting instructions from the RAM.
Located very near to the CPU.
Doesn’t take as much time as it doesn’t need to fetch the instructions from the RAM.
What is clock speed?
Sends a pulse at fixed intervals to trigger the next stage of the FDE cycle.
Name some factors of clock speed.
The higher the clock speed, the more pulses are sent per second, so more instructions can be executed.
What is a core?
A complete copy of a CPU.
Name some factors of the number of cores.
Each core has it’s own ALU and CU, having multiple cores allows a CPU to process multiple instructions at the same time.